1. Field of the Invention
The present invention relates to a computerized radiography device, and more particularly, a system for and method of reading out a storage phosphor screen using a pulsed semiconductor light source array which can be applied to a radiation diagnostics system, a dental radiation diagnostics system, an auto-radiography system, a image detection system by an electron microscope, a radiation diffraction image detection system, and a fluorescence detection system for life science analysis, which all use a storage phosphor screen (or a storage phosphor sheet or an imaging plate).
2. Description of the Related Art
A radiation sensor used in a radiography system employing a storage phosphor screen is constructed in such a fashion that a microcrystalline film made of bromine barium fluoride (BaFBr:X, X is halogen) as a luminescent material is coated in the thickness of approximately 80-150 xcexcm on a polyester film having a thickness of approximately 150 xcexcm, and then the coated microcrystalline film is covered with an approximately 10 xcexcm thick polyethylene terephthalate film. When such a luminescent film is irradiated by radiation, energy of radiation which has transmitted an examination subject is stored and recorded on the storage phosphor material while forming a latent image. At this time, when the storage phosphor material on which the latent image is formed is illuminated by a micro light source of a specific wavelength band, a photo-stimulated luminescence according to the stored radiation energy is generated. There is well-known a radiation diagnostics system in which the illuminating position of the micro light source and the intensity of the luminescence light are converted into a digital signal for reconfiguration so that a digital image signal is produced, then the digitized image is processed further in a computer, following which a radiological image is produced on a display unit such as a monitor or a recording material such as a photographic film and the like (see Japanese patent laid-open publication Nos. Sho 55-12429, Sho 55-116340, Sho 55-163472, Sho 56-11395, etc.).
There is also well known an image detection system by an electron microscope in which the identical photo-stimulatible phosphor is used as a radiation detecting material, and after a material which is granted a radioactive mark is charged into a living body, by using the living body or a part of a tissue of the living body as a specimen, a storage phosphor screen on which the phosphor layer is formed is overlapped with the specimen during a certain period of time so that radiation energy is stored and recorded in the phosphor layer. At this time, the storage phosphor screen is scanned by illumination of a light source of a specific wavelength band (633 nm or 635 nm) so that an image of the living body""s tissue is detected. Further, a radiation diffraction image detection system is well known in which a structure analysis of the specimen, etc. is conducted (see Japanese patent laid-open publication Nos. Sho 61-51738, Sho 61-93538, Sho 59-15843, etc.).
Unlike a case of using a conventional photographic film, a system employing such a storage phosphor screen as an image detecting element has several advantages in that it eliminates the necessity of a chemical process such as development of a photographic film, and an acquired image material experiences an image process so that both reproduction and quantitative analysis of an image for a specific portion are possible.
In addition, in an auto-radiography system, a fluorescence detecting system is well known which substitutes a fluorescent material for the radioactive mark material. According to such a fluorescence detecting system, the readout of a fluorescent image allows evaluation and analysis for a gene arrangement, a revelation phase of a gene, the path of metabolism and absorption, excretion, the state of charged material, separation, classification or molecular weight, and properties of a protein in an experimental mouse. For example, after a fluorescent pigment is applied to a solution containing a lot of pieces of DNA, the DNA pieces undergo cataphoresis properly following a gel support, or the DNA pieces undergo cataphoresis following the gel support having the fluorescent pigment contained therein and the gel support being immersed in a solution containing the fluorescent pigment. Then, after the DNA pieces that have undergone the cataphoresis are marked, the fluorescent pigment is stimulated by a micro light of a specific wavelength (488 nm) so that fluorescence is generated from the samples like the DNA pieces. An image is formed through the detection of the generated fluorescence, and analysis of DNA arranged on the gel support is possible. Such a fluorescence detecting system has advantages in that the necessity of using a radioactive material is eliminated and it is possible to simply detect a gene arrangement.
Like this, there is well known a conventional readout technology which has been proposed to acquire distribution of a two-dimensional position of a luminescence light signal from a storage phosphor by using a radioactive material or a fluorescent material as a radioactive label material. The conventional readout technology is classified into five following methods:
(i) a method in which a storage phosphor screen is scanned in the X-axis direction by a laser beam through a reflection mirror with the phosphor screen being moved in the Y-axis direction to acquire the distribution of a two-dimensional position (see U.S. Pat. No. 4,973,134, etc.).
(ii) a method in which a storage phosphor screen which is fixed is scanned in the X and Y-axis directions by a laser beam through two reflection mirrors, and a luminescence signal is collected in a photomultiplier tube by another reflection mirror to acquire the distribution of a two-dimensional position (see U.S. Pat. No. 5,124,558, etc.).
(iii) a method in which a screen is fixed and a readout head composed of a laser light source and a collection lens is moved in the X and Y-axis directions to acquire the distribution of a two-dimensional position.
(iv) a method in which an image detection material including a disk type storage phosphor (also referred to storage phosphor disk) like a CD-ROM is proposed, and the rotatable storage phosphor disk is read out by the same principle as that of CD-ROM to acquire the distribution of a two-dimensional position (see U.S. Pat. No. 5,144,135, etc.).
(v) a method in which a position-sensitive photosensor such as ICCD (Intensified Charged Coupled Device) or PSPMT (Position Sensitive Photomultiplier) and the like is substituted for a single photomultiplier applicable to a general storage phosphor screen readout apparatus, and a xenon arc lamp or a halogen flash lamp coupled to a beam homogenizing filter is used as a simulating light source to acquire the distribution of a two-dimensional image position (see U.S. Pat. No. 5,864,146, etc.).
In the above conventional prior art, a monochromatic laser as a point light source and a line source is used for photostimulation of a storage phosphor screen (or an image carrier such as a storage phosphor sheet or an imaging plate or a gel support or a transcription support, etc.), and a method is employed in which a light stimulating section or a light collecting section is moved in the X and Y axis directions to acquire the distribution of two-dimensional position, thus a long time readout is necessary to obtain a suitable resolution. On the contrary, in the case of using a position-sensitive light collecting device, since the xenon arc lamp or the halogen flash lamp as the light stimulating section is used in parallel with an optical filter or the beam homogenizing filter, a physical movement of the device becomes unnecessary so that a time required for the readout is reduced. However, the prior art has a limitation in a spatial resolution and a manufacturing cost of the device is expensive.
Moreover, the radiation diagnostics system, the auto-radiography system, the image detection system by an electron microscope, the radiation diffracted image detection system, and the fluorescence detection system use such a storage phosphor screen as an image detecting medium. Since these systems scan a storage phosphor element bearing an image with an excitation light, detect luminescence from the image carrier to produce an image, and perform a diagnosis or detection, the storage phosphor screen readout device is preferably constructed to use a tunable wavelength, if necessary.
Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a system for and method of reading out a storage phosphor screen in which a wavelength of a readout light can be varied easily by a wavelength-tunable light source, which eliminate vibration and noise according to a conventional storage phosphor screen readout method allowing physical circulation on the X-Y axis of a light source, and which enable a high readout operation and acquisition of a high quality image by using an electrically controllable photostimulation method and can be implemented at a low price.
According to one aspect of the present invention, there is provided a method of reading out a storage phosphor screen (or an image carrier such as a storage phosphor sheet or an imaging plate and the like) which is sensitive to radiation and is applicable to an industrial non-destructive inspection system, a medical radiation diagnostics system, a dental radiation diagnostics system, an auto-radiography system, a image detection system by an electron microscope, a radiation diffracted image detection system, and a fluorescence detection system for life science analysis and the like, comprising the steps of:
optically stimulating the storage phosphor screen to induce luminescence according to a response to radiation to acquire a digital image of a subject from the storage phosphor screen by using a semiconductor light source array as a stimulating light source to which an optical fiber array consisting of a bundle of optical fibers having diverse forms is connected;
controlling a starting of the semiconductor light source array with an electric pulse; and
interlocking a semiconductor light source array starting pulse for generating a stimulating light with a photomultiplier tube for collecting a luminescence light signal induced from the storage phosphor screen by the stimulating light to represent the collected luminescence light as distribution of a two-dimensional position to acquire the digital image of the subject from the storage phosphor screen.
According to another aspect of the present invention, there is also provided a system for reading out a storage phosphor screen (or an image carrier such as a storage phosphor sheet or an imaging plate and the like) which is sensitive to radiation and is applicable to an industrial non-destructive inspection system, a medical radiation diagnostics system, a dental radiation diagnostics system, an auto-radiography system, a image detection system by an electron microscope, a radiation diffracted image detection system, and a fluorescence detection system for life science analysis and the like, comprising:
a storage phosphor screen adapted to form a latent image of a subject as a radiation or a fluorescent material is irradiated to the subject or labeled;
an image processing computer adapted to control the starting of the storage phosphor screen readout system to read out the latent image of the subject formed on the storage phosphor screen, and to re-configure a collected image data to process the image so that an optimum image of the subject is produced;
a time interlocking signal processing module adapted to generate a main signal pulse having a certain period when the time interlocking signal processing module is supplied with a starting signal of the storage phosphor screen readout system from the image processing computer, to store the collected image data in a buffer included therein, and to transfer the image data collected and stored in the buffer to the image processing computer when one readout process is completed;
a semiconductor light source starting module adapted to generate a pulse for sequentially starting a semiconductor light source on the basis of the main signal pulse generated from the time interlocking signal processing module;
a semiconductor light source array including a plurality of semiconductor light sources which is started sequentially by the pulse generated from the semiconductor light source starting module to generate a stimulating light necessary for reading out the latent image of the subject formed on the storage phosphor screen;
a plurality of light transmitting lenses adapted to collect the stimulating light generated from the semiconductor light source array;
a stimulating light transmitting optical fiber adapted to allow the stimulating light passing through the plurality of light transmitting lenses to be transmitted;
an optical fiber array adapted to scan the storage phosphor screen with the stimulating light transmitted thereto through the stimulating light transmitting optical fiber, the optical fiber array being adapted to collect a luminescence light induced from the front surface of the storage phosphor screen through the scan of the storage phosphor screen by the stimulating light;
a collected light transmitting optical fiber adapted to allow the luminescence light collected by the optical fiber array to be transmitted;
a main photomultiplier tube adapted to collect, filter and multiply the luminescence light transmitted thereto from the optical fiber array through the collected light transmitting optical fiber;
a main photomultiplier tube starting module adapted to start the main photomultiplier tube, the main photomultiplier tube starting module being adapted to amplify and digitize a signal of the luminescence light collected by the main photomultiplier tube;
an auxiliary photomultiplier tube adapted to collect, filter and multiply a luminescence light induced from the rear surface of the storage phosphor screen through the scan of the storage phosphor screen by the stimulating light; and
an auxiliary photomultiplier tube starting module adapted to start the auxiliary photomultiplier tube, auxiliary photomultiplier tube starting module being adapted to amplify and digitize a signal of the luminescence light collected by the auxiliary photomultiplier tube.